The invention relates to apparatus for electrical discharge machining of an electrode workpiece by way of a plurality of electrode tools, and which comprises a storage magazine for storing the electrode tools and a movable carriage provided with support means for transporting the electrode tools between the magazine and the tool holders mounted on the end of the ram or quill of the apparatus.
It is often necessary, in order to machine a workpiece of complex shape, to use consecutively several electrode tools of different shapes, for example a large size electrode tool for sinking a cavity, and a small size electrode tool for machining a small detail in the cavity. It is known to provide an EDM apparatus, when such an operation is required, with a single electrode tool holder and to provide all the electrode tools with a matching support or mount member such that diverse sizes of electrode tools can be handled by an automatic tool changer.
However, it is very difficult to design an electrode tool holder which is convenient for holding small electrodes as well as large electrodes, and which provides constant sufficient rigidity and precision of positioning of the electrode tools irrespective of their size or shape.